Air-cooled turbine buckets



Feb. 18, 1958 D. GERDAN ETAL AIR-COOLED TURBINE BUCKETS 3 Sheets-Sheet 1Filed June 9, 1952 ,21227 2, mzwy Attorneys Feb. 18, 1958 n. GERDAN ETAL2,823,894

AIR-COOLED TURBINE BUCKEI'S 3 sheets sheet 2 Filed June 9, 1952Inventors flew a7? & 22222 J.

Attorneys wild! Feb. 18, 1958 D. GERDAN EIAL 2,823,894

AIR-COOLED TURBINE BUGKETS Filed June 9,, 1952 r 3 Sheets-Sheet 3 6lyentgs 142/ 2 a: an 4 42) 217222220 5.

' Attorneys AIR-COOLED TURBINE BUCKETS Application June 9, 1952, SerialNo. 292,547

12 Claims. (Cl. 253-3915) Our invention relates to fluid-directingelements for turbomachines such as are generally known by the termsbuckets, blades and vanes and, more particularly, to those which areadapted for use in axial flow compressors or turbines of known type.

The invention has particular relation to turbines of high temperaturetypes, since one of the primary objects of the invention is to provide abucket or the like which is particularly adapted for cooling.

It is generally recognized that the principal factor limiting theefficiency and power output of gas turbines is the limited temperatureof the motive fluid imposed by the turbine buckets. It has long beenrealized that adequate provision for cooling turbines buckets could bebeneficial either in increasing the temperature limitation of the engineor in permitting reduced use of critical materials, or both. As aresult, many proposals for structures adaptable for cooling have beenadvanced and some have been used to some extent. Despite the long periodof awareness of the need for a satisfactory cooled bucket, progress inthis respect has not been satisfactory.

The principal objects of our invention are to provide a turbine bucketor the like having superior characteristics so far as cooling isconcerned, which is of high strength, and which is readily adapted tosimple production techniques.

This result is attained by the use of sheet metal for the major portion,if not all, of the bucket. A particular feature of the invention is theutilization of laminated sheet metal construction for the major part ofthe bucket, the laminae being so disposed as to provide channels forcooling air. This invention is related to those described and claimed inour copending applications for Turbine Buckets, Serial No. 292,545,filed June 9, 1952, and Laminated Turbine Buckets, Serial No. 292,546,filed June 9, 1952. The subject mater of this application differs fromthose of the copending applications primarily in differences in thestructure to provide modified arrangements for circulating cooling airthrough the buckets. A feature of the present invention is a provisionfor diverting cooling air from the laminated structure which forms thecentral portion of the blade chordwise to the portions of the bladeadjacent the leading and trailing edges. Another feature of the presentinvention lies in providing a laminated structure such that the path forflow of air is somewhat tortuous so that greater turbulence is set up inthe current of cooling air flowing through the blade.

The principal objects of the invention are to provide a turbine bucketor other flow deflecting element for use in turbomachines which isparticularly well adapted for cooling, which is strong and light inweight, and which may be conveniently manufactured, both from thestandpoint of the convenience of the process of manufacture, and thereduction in the requirements of critical materials for the buckets.

The nature of the invention, the advantages thereof, and the preferredmanner in which the objects are realized, will be apparent to thoseskilled in the art from the sucnited States Patent T 2,823,894 PatentedFeb. is, 1958 ceeding detailed description of preferred embodiments ofthe invention and the accompanying drawings, in which Fig. 1 is alongitudinal section of a turbine bucket in accordance with theinvention, mounted in a fragmentary portion of a turbine wheel, thesection being taken approximately on the main camber line of the blade;Fig. 2 is a partial longitudinal section thereof taken on the plane 2-Zindicated in Fig. i; Fig. 3 is a transverse section of the same taken onthe plane 33 indicated in Fig. 1; Fig. 4 is a longitudinal section ofthe same taken on the plane 4-4 indicated in Fig. 1; Fig. 5 is asectional view similar to that of Fig. 1 of a modified form of blade;Fig. 6 is a longitudinal section thereof taken on the plane 66 indicatedin Fig. 5 and Figs. 7 and 8 aretransverse sectional views taken on theplanes 77 and 88, respectively, indicated in Fig. 5.

Referring first to Figs. 1 to 4, the turbine bucket comprises a bladeportion A and a base portion B, the latter being mounted in the rim of aturbine wheel C. The blade may be mounted in any suitable manner as bythe conventional multiple dovetail arrangement illustrated in Fig. 2 inwhich the turbine wheel is formed with a serrated slot 11 and the bladeroot is provided with serrations or dovetails 12 engaging in the wheel.The base B comprises a central part of laminated construction and endblocks 13 and 14. The laminated structure extends from the base portionof the bucket into the blade portion to constitute a core for the bladeportion, most of the laminae extending to the tip of the blade, thelaminated structure defining the central part of the blade.

The laminae are of several types so that when stacked and brazedtogether they define passages for circulation of cooling air from thebase of the bucket to the tip. The laminae 16 of the first group extendfrom one face of the blade to the other, the edges of these laminaeconstituting elements of the outer surface of the blade and rootportions. Between adjacent laminae 16 are disposed perforated laminae 17and 1.8. One of the laminae 17 is shown in section in Fig. 4. The edgesof the laminae 17 and 18 also form elements of the sides of theassembly. The outer end of the lamina 17 is bifurcated as indicated at21 and a number of openings 19 are distributed along the length. Theseopenings are preferably as wide as the thickness of the blade willpermit. The typical lamina 18, shown behind the lamina 17 in Fig. 4, isformed with openings 22 similar to the openings 19 in the lamina 17 butdisposed so as to overlap an dextend beyond the bridge portions betweenthe openings 19. The outer end of the laminae 18 are cut out orbifurcated as indicated at 23. Thus, a continuous passage for flow ofair is provided between the adjacent laminae 16 of the first group bythe overlapping openings 19 and 22 of the intermediate laminae.

Air is supplied to the passages from a. chamber 26 in the base of thebucket through passages 27 provided by bifurcating the base portion ofthe laminae 17 and 18.

The air fiows from the passage 27 into passages 28 in the laminae 17 and29 in the laminae 18 from which it continues upward to the tip of theblade. All the laminae 16 are punched to provide a continuous passage 30extending through the stack of laminae.

Air may be supplied to the chamber 26 in any convenient manner, as by apassage 31 in the turbine wheel.

The portions of the fluid-directing service blade ahead of the foremostlamina 16 and rearwardly of the rearmost lamina 16 are defined generallyby V-shaped sheet metal pieces 32 and 33 which thus define the leadingand trailing edge portions of the blade surface, respectively. Theseparts 32 and 33 are brazed or welded to the abutting laminae 16 and tothe end blocks 13 and 14. It may be noted that the blocks 13 and 14 areformed with projections 36 and 37 extending from their upper 32 and 33,thus additionally locating these parts and providing a greater surfacefor brazing to withstand the centrifugal force pull along these partswhen they are mounted on a rotating wheel.

It will be noted that the portions 32 and 33 of the blade define spacesor passages 32. and 33' within them which provide for circulation ofcooling air out the open tip of the blade. A feature of the invention isthe arrangement for distributing cooling air into these spaces orpassages at points distributed along the length of the passage.Referring to the leading edge portion of the blade, it will be notedthat immediately adjacent the foremost lamina 16 is a lamina 41 whichextends nearly to the tip of the blade and which is open through themiddle except at the extreme outer end of the lamina. Adjacent thelamina 41 is a lamina 42 which extends from wall to wall of the sheet 32and is unbroken except for a number of cooling air outlets 43 in theouter half of the blade length. Thus, air may be brought through thechannel 44 defined by the laminae 42, 41 and 16 and discharged throughthe openings 43. A second set of laminae 46 and 47 abutting the lamina42 similarly distribute air into the portion of the blade nearer thebase. A further set of laminae 48 and 49, which are quite short, providefor discharge of air into passages 32' and 33 immediately adjacent thesolid base portion 13 of the blade. This structure will be more clearlyapparent from the illustration of the laminae 47 and 49 in Fig. 2, thelamina 42 being similar. It will thus be seen that air is dischargedfrom a number of openings distributed along the span of the blade tocool the leading edge portion. A similar laminated structure 41, 42, 46,47, 48, 49 is disposed Within the trailing edge portion 33 to cool it insimilar manner.

In summary, it will be seen that each two juxtaposed laminae 17 and 18constitute a set of laminae the overlapping openings in which define acontinuous (that is, unbroken) conduit for cooling medium extendingthrough the core. the blade are mutually spaced from laminae 42, laminae42 are mutally spaced from laminae 47, and laminae 47 are mutuallyspaced from laminae 49. Conduits for cooling air are thus definedbetween laminae 49 and 47, between laminae 47 and 42, and betweenlaminae 42 and the adjacent laminae 16. This cooling air is dischargedthrough the openings in laminae 49, 4'7, and 42 into the passages 32 and33. Laminae 16 may also be regarded as mutually spaced, being spaced bythe intervening y laminae 17 and 18.

The form of air cooled bucket shown in Figs. to 8, inclusive, differsfrom that previously described in several respects. The outer surface orsheath of the blade is entirely defined by a sheet metal sheath whichextends from the leading edge to the trailing edge of the blade. Also,the laminated structure of the central portion of the blade is ofdifferent type. The provision for directing air to the leading andtrailing edge portions of the blade, however, is the same as in theembodiment previously described.

Parts shown in Figs. 5 to 8 which are the same as those previouslydescribed are identified by the same reference numerals and do notrequire detailed description. Alternate laminations in the central partof the blade identified as 51 extend from end to end of the blade andfrom interior wall to interior wall of the blade sheath 50, which sheathmay be formed of two sheets brazed or welded together at the leading andtrailing edges as illustrated. In the base of the blade, only, thelaminae 51 have between them laminae 52, each of which is initwo parts(Fig. 6), each part forming a part of one of theserrated faces of theblade root. The two parts of the laminae 52 define a cooling air channel53 between the opposed edges thereof, which is also bounded by the facesof the laminae 51. v A passage 30 extend- The laminae 16 nearest theedges of ing through the laminae interconnects the passages 53 andconnects them with channels 54 defined by the spaces between the laminae51. The passages through the blade root are thus similar to those of theprevious form except that each passage is defined by a single lamina.The laminated structure includes laminae 41, 42, 46, 47, 48, and 49 atboth the leading and trailing edges, which may be identical to thosepreviously described. A lamina 42 is shown in section in Fig. 6,illustrating the openings -43 therein for discharge of air into thetrailing edge portion of the blade. It will be understood that thelaminations are stacked and brazed together, and that the sheath 50 isfitted to the laminated portion structure and brazed thereto as well asto the blocks 13 and 14 of the base.

It will be seen from the foregoing that the forms of sheet metal bladestructure described herein are particularly well adapted to provide astrong structure and provide adequate cooling of the entire bladeportion which is subject to the effect of a hot motive fluid.

While we have described in detail the preferred embodiments of ourinvention for the purpose of illustrating the principles thereof, it isto be understood that various modifications may be made within the scopeand principles of the invention, which is not to be considered aslimited by the detailed description.

We claim:

1. A fluid-directing blade for turbomachines and the like, said bladehaving fluid-directing faces and comprising a number of laminaeextending in the directions lengthwise of the blade and from face toface of the blade, at least some of said laminae defining a core for theblade, the blade also comprising leading and trailing edge portionsabutting the core and recessed adjacent the core to define with the corepassages for a cooling medium extending lengthwise of the blade Withinthe leading and trailing edge portions, the laminae of the core beingmutually spaced to define conduits for the cooling medium within thecore lengthwise of the blade, the laminae adjacent the said passagesbeing formed with openings to direct cooling medium from the conduitsadjacent the last-mentioned laminae into the passages.

2. A fluid-directing blade as recited in claim 1 in which the edges ofat least some of the laminae constitute elements of the fluid-directingfaces of the blade.

3. A fluid-directing blade for turbomachines and the like, said bladehaving fluid-directing faces and comprising a number of laminaeextending in the directions lengthwise of the blade and from face toface of the blade, at least some of said laminae defining a core for theblade, the blade also comprising leading and trailing edge portionsabutting the core and recessed adjacent the core to define with the corepassages for a cooling medium extending lengthwise of the blade withinthe leading and trailing edge portions, the laminae of the core adjacentthe passages being mutually spaced to define conduits for the coolingmedium within the core lengthwise of the blade, the laminae adjacent thesaid passages being formed with openings to direct cooling medium fromthe conduits adjacent the last-mentioned laminae into the passages, andthe laminae of the core remote from the passages being provided in setswith overlapping staggered openings therein to define sinuous conduitsfor cooling medium through the core, each said set comprising at acontinuous sinuous conduit for cooling medium extending lengthwise ofthe blade.

5. A fluid-directing blade for turbomachines and the like, said bladehaving fluid-directing faces and comprising a number of laminaeextending in the directions lengthwise of the blade and from face toface of the blade, some of the laminae being formed with openingstherethrough, the openings in mutually adjacent ones of said somelaminae constituting a set being in staggered overlapping relation sothat the openings define a continuous sinuous conduit for cooling mediumextending lengthwise of the blade, and laminae without openings beingprovided between each set of the laminae with openings.

6. A fluid-directing blade for turbomachines and the like, said bladehaving fluid-directing faces and comprising a number of laminaeextending in the directions lengthwise of the blade and from face toface of the blade, at least some of said laminae defining a core for theblade, the blade also comprising leading and trailing edge portionsabutting the core, at least some of the laminae of the core being formedwith a plurality of openings therethrough, and the openings in mutuallyadjacent ones of said some laminae being in staggered overlappingrelation so that the openings define a continuous conduit for coolingmedium extending lengthwise of the blade.

7. A fluid-directing blade for turbomachines and the like, said bladehaving fluid-directing faces and comprising a number of laminaeextending in the directions lengthwise of the blade and from face toface of the blade, at least some of said laminae defining a core for theblade, the blade also comprising leading and trailing edge portionsabutting the core and recessed adjacent the core to define with the corepassages for a cooling medium extending lengthwise of the blade withinthe leading and trailing edge portions, at least some of the laminae ofthe core being formed with a plurality of openings therethrough, and theopenings in mutually adjacent ones of said some laminae being instaggered overlapping relation so that the openings define a continuoussinuous conduit for cooling medium extending lengthwise of the blade.

8. A fluid-directing blade for turbomachines and the like, said bladehaving fluid-directing faces and comprising a number of laminaeextending in the directions lengthwise of the blade and from face toface of the blade, at least some of the laminae being formed with aplurality of openings therethrough, and the openings in mutuallyadjacent ones of said some laminae being in staggered overlappingrelation so that the openings define a continuous sinuous conduit forcooling medium extending lengthwise of the blade alternately through onelami-' nation and the other of said some laminae.

9. A fluid-directing blade for turbomachines and the like, said bladehaving fluid-directing faces and comprising a number of laminaeextending in the directions lengthwise of the blade and from face toface of the blade, at least some of said laminae defining a core for theblade, the blade also comprising an edge portion abutting the core andrecessed adjacent the core to define with the core a passage for acooling medium extending lengthwise of the blade within the said edgeportion, the

laminae of the core being mutually spaced to define conduits for thecooling medium within the core lengthwise of the blade, the laminaeadjacent the said passage being formed with openings to direct coolingmedium from the said conduits adjacent the last-mentioned laminae intothe passage.

10. A fluid-directing blade for turbomachines and the like, "said bladecomprising a number of laminae extending lengthwise of the blade, thelaminae comprising at least one set of two juxtaposed laminae, providedwith spaced openings therethrough, the openings in the respective onesof said set being in staggered overlapping relation to define acontinuous conduit through the openings alternating from one lamina ofthe set to the other.

11. A blade as recited in claim 10 in which the openings are disposedfrom end to end of the blade so that the said conduit extends from endto end of the blade.

12. A fluid-directing blade for turbomachines and the like, said bladehaving fluid-directing faces and comprising a number of laminaeextending in the directions lengthwise of the blade and from face toface of the blade, at least some of said laminae defining a core for theblade, the blade also comprising a tubular sheath covering the core ofthe blade and abutting the core, the sheath including leading andtrailing edge portions spaced from the core to define with the corepassages for a cooling medium extending lengthwise of the blade withinthe leading and trailing edge portions, the laminae of the core beingmutually spaced to define conduits for the cooling medium within thecore lengthwise of the blade, the laminae adjacent the said passagesbeing formed with openings to direct cooling medium from the conduitsadjacent the last-mentioned laminae into the passages.

Atkinson Oct. 7, 1952 Kane Nov. 18, 1952

